The Common Cold, Allergies and Dehydration: Fluids to Avoid

Dehydration risks may increase when we have the common cold or respiratory tract infections (RTIs) because we are less likely to consume water.

However, a 2011 review of research found there is no conclusive evidence that increased fluid consumption (greater than required to hydrate) will assist in the management of an illness.

This is despite common belief that drinking more fluids when sick is important to replace fluids lost from fever or rapid breathing and to reduce the viscosity of mucus.

The review found that no randomised controlled trials have been conducted on the benefit or harm of consuming extra fluids while sick and recommends further studies to “determine the true effect of this very common medical advice”.

Furthermore, the review states that there are potential dangers in consuming excessive amounts of water as salt levels in the blood may become too low causing headache, confusion and seizures and the potentially fatal outcome of cerebral oedema in a condition known as hyponatremia.

While excessive consumption of fluids may not apply, generally accepted broad fluid consumption recommendations do. They call for around 2.6 litres, or about 10, 250ml glasses of water each day, along with a balanced diet.

How Different Fluids Influence Illness

Hot Fluids:

There is some evidence that drinking hot fluids may be superior to drinking cold fluids in the management of the common cold and RTIs by increasing ‘nasal mucus velocity’ – the body’s ability to break down and expel mucus. However that may be due to the steam inhaled while drinking, rather than the ingestion of the hot fluid itself.

The study also found that cold water significantly decreased ‘nasal mucus velocity’.

Dairy: the Jury is still out

Traditional thinking has stated that dairy should be avoided if you have a cold, allergies or asthma because it increases mucus production.

However multiple studies have found that milk consumption has no effect on mucus production or asthma, although there are some documented cases where an allergy to cow’s milk produced asthma-like symptoms.

Despite this, a 2009 study found that the type of milk consumed has an impact. They state that A1 milk with “beta-casomorphin-7 (beta-CM-7), an exorphin derived from the breakdown of A1 milk, stimulates mucus production from gut MUC5AC glands”.

A recent boom in sales of A2 milk in Australia has occurred due to its positioning as a better option for allergy suffers.

Alcohol: to drink or not to drink

The belief that consuming alcohol, such as a glass of brandy or a hot toddy (whisky with hot water and lemon juice), will ‘kill a cold’ or reduce the severity of a cold is a myth. While you might feel better initially, that’s probably because you’re getting drunk.

Furthermore, alcohol often does not mix well with the medications or antibiotics taken for the treatment of an illness and consuming it will probably also increase the severity and longevity of that illness by causing dehydration.

Studies have also found that alcohol can often worsen allergies, such as asthma and hay fever – particularly among women, not because of the alcohol itself but because of the histamines and sulfites contained in the drinks.

However it’s not all bad news. A 1993 research paper studied 391 subjects who were intentionally exposed to one of five respiratory viruses along with 26 subjects who were given saline. They found that drinking 3-4 alcoholic drinks each day decreased susceptibility to colds.

Another study of 4272 people found that beer and spirits consumption did not have this effect. However it did find that consuming more than an average of 14 glasses of wine each week (two each night presumably, not 14 in one sitting) resulted in a cheers-worthy 60% reduction in the occurrence of the common cold compared with teetotallers, probably because of the wine’s antioxidants.

However given the many other negative effects of alcohol, it’s probably better to use other methods for fighting illness.